Medical cardiac pacemaker



Oct. 9, 1962 w. GREATBATCH 3,057,356

MEDICAL CARDIAC PACEMAKER Filed July 22, 1960 INVENT OR WILSONGREATBATCH ATTORNEY United States Patent Ofifice I 3,057,356 PatentedOct. 9, 1962 3,057,356 MEDICAL CARDIAC PACEMAKER Wilson Greatbatch,Clarence, N.Y., assignor to Wilson Greatbatch Inc., Clarence, N.Y., acorporation of New York Filed July 22, 1960, Ser. No. 44,796

4 Claims. (Cl. 128-422) This invention relates to medical prostheticdevices generally, and more particularly to an improved medical cardiacpacemaker.

Recent advances in modern medical science have made feasible thesubstitution of a mechanical or electrical element in place of adiseased or non-functional organ within the human body. In view of thesemedical advances, a demand has arisen for instruments capable ofperforming physiological functions previously performed by natural humanorgans. The prevalence of hear-t disease and the indispensible functionsof the human heart as a life sustaining organ have made the developmentof instruments which are capable of affecting the function of the heartof paramount importance.

The heating of the heart is controlled by electrochemical nerve signalswhich originate at the sinus node, sometimes called the pacemaker. Thisnode generates approximately 72 electrical pulses per minute whichtravel in an electrical chemical manner over the nerve networks of theheart. One group of nerves distributes the pacemarker signal over thesurface of the auricle, causing the contraction of the auricle and thefilling of the ventricle. Another group of nerves, called theauricular-ventricular or AV bundle, carries the pacemaker signal downthrough the septum and, after about a 0.1 second delay, distributes itover the ventricle. This causes a slightly delayed contraction whichthen pumps blood into the arterial system of the body. If theauricularventricular bundle becomes incapacitated, the pacemaker signalno longer reaches the venticle, and the ventricle reverts to a beatingrhythm of its own which is much slower than the pacemaker rate. If thisidioventricular rhythm, or beating rhythm of the ventricle, drops below40 beats per minute, the patient will usually suffer periodic faintingspells, while if the rate drops below 30 beats per minute, permanentbrain damage or death may result. When damage or incapacitation of theauricularventricular bundle is incurred, it is desirable to provide anartificial electronic pacemaker which is capable of furnishing a signaldirectly to the surface of the ventricle.

Artificial cardiac pacemakers presently in use have requiredconsiderable power and have either been incapable of operating from abattery power source or have required frequent battery replacement. Thesize and power requirements of the presently existing cardiac pacemakershave precluded the implantation of the device within the human body,thus necessitating external mountings with transmission wires passingthrough the skin of the patient. These restrictions, inherent in priorartificial pacemaker devices, have contributed to patient discomfort andincapacitation, and additionally have given rise to the possibility ofinfections and other dangers which might accompany a permanent orsemi-permanent penetration of the human body shell by a foreign object.

The primary object of this invention is to provide an improvedartificial cardiac pacemaker for restoring satisfactory heart rhythm toa heart which is functioning inadequately due to conduction defects inthe auricularventricular bundle.

Another object of this invention is to provide an artificial cardiacpacemaker requiring low power consumption, so that battery operation isfeasible for long uninterrupted periods without battery replacement.

Another object of this invention is to provide an artificial cardiacpacemaker which may be directly connected to the surface of theventricle of the heart.

A still further object of this invention is to provide an artificialcardiac pacemaker which is constructed from materials compatible to thebody environment and is of such an electrical and mechanicalconfiguration, that permanent implantation of the device within thehuman body is both feasible and practical.

With the foregoing and other objects in view, the invention resides inthe following specification and appended claims, certain embodiments anddetails of construction of which are illustrated in the accompanyingdrawings in which:

FIG. 1 illustrates a circuit diagram of the artificial cardiac pacemakerof the present invention;

FIG. 2 shows a circuit diagram of an embodiment of the invention ofFIGURE 1 which is capable of operation at higher powers; and

FIG. 3 is a perspective view of the circuit enclosing envelope and pulsesupplying electrodes of the present invention.

Basically, the cardiac pacemaker of the present invention includes apulse forming oscillator circuit indicated generally at 10 in FIG. 1which is cast into a hard epoxy compound and then covered with a thincoating of silicone rubber, which is compatible to the environment ofthe human body, to for-m an envelope 11 illustrated by FIG- URE 3. Awire 12, also insulated with silicone rubber, transmits the pulses fromthe circuit 10 contained within the envelope 11, to stainless steelelectrodes 13. It is obvious that the pacemaker of the subject inventionneed not be limited to construction from the aforementioned materials,but that any materials compatible so the environment of the human bodymight be utilized.

The physical configuration of the artificial pacemaker as illustrated byFIG. 3 provides inherent features of minimum size and weight to makefeasible the complete implantation of the device within the human body.The envelope 11 is approximately 2% inches in diameter and A inch thick,and is therefore a thin, wafer-like construction. The total weight ofthe pacemaker is approximately 4 ounces. In use, the electrodes 13 maybe implanted in the ventricle of the heart, while the envelope 11 may beimplanted outside the rib cage but under the skin, where it will beaccessible for battery replacement as required.

The pacemaker circuit 10 of FIG. 1 generates a square pulse ofapproximately 10 volts amplitude and approximately one millisecondduration. The circuit is capable of delivering a pulse of over threemilli-amperes into cardiac tissue.

Referring now to FIG. 1, the pacemaker circuit 10 consists of a timingtransistor 14 having a collector electrode 15, base electrode 16, and agrounded emitter electrode 17. The collector electrode 15 of thetransistor 14 is serially connected to the primary winding 18 of afeedback transformer 19. Feedback transformer 19 includes a secondarywinding 20, which is electrically connected through a timing capacitor21 to the base 16 of the transistor 14. The base electrode 16 of thetransistor 14 is also connected to the primary winding 18 of thefeedback transformer 19 by means of a resistor 22 which, acts inconjunction with the capacitor 21, to form a timing circuit. Thus, thefeedback transformer 19 couples the output signal from the transistor 14to the timing circuit formed by the capacitor 21 and the resistor 22. Aunidirectional voltage source 23 provides voltage through the primary 18of the feedback transformer 19 to the collector 15 of the transistor 14.An output lead 25 transmits a pulse from the collector 15 of thetransistor 14 to a spot on the ventricular wall of the human heart,while a lead 3 25 connects a reference ground potential to an adjacentspot on the ventricular wall of the heart.

In the operation of the invention as illustrated by FIGURE 1, thereference potential at the collector 15 of the transistor 14 dropssuddenly to reference ground potential when the transistor becomesconducting. This causes a positive pulse to be applied to the outputlead 24 and also across the feedback transformer 19 to the capacitor 21and the base electrodes 16 of the transistor 14. This voltageapplication to the base 16 of the transistor drives the transistor '14to saturation and thus continues to hold the collector electrode 15 atground potential. After a predetermined period of time, in this caseapproximately one millisecond, the capacitor 21 becomes completelycharged, and simultaneously, the induced voltage at the secondarywinding 20 of the transformer 19 begins to decay. This causes a reversalin the voltage at the base electrode 16 of the transistor 14, suchreversal being amplified by the transistor and fed back through thetransformer 19 and the capacitor 21 to the base electrode 16 of thetransistor 14 to cause the flow of all collector current through thetransistor to be out 01f. The transistor is held in this cut-off stateby the accumulated charge on the capacitor 21 until the capacitor chargeis drained off by the resistor 22. This resultant time delay isproportional to the product of the resistance of the resistor 22 and thecapacity of the capacitor 21, and in particular pacemaker circuits maybe equal to about one-tenth of this product. Thus by utilizing specificvalues of capacitance and resistance, an R-C product of approximatelyseconds may be obtained to produce a repetition rate of approximatelyone pulse per second. It is obvious that by varying the resistance andcapacitance values of the resistor 22 and the capacitor 21, variouspulse repetition rates might be ob tained. It is also feasible tosubstitute a potentiometer for the resistor 22, so that the pulserepetition rate of the circuit 10 might be adjustably controlled inorder to vary the rhythm of a defective human heart.

FIGURE 2 illustrates a pulse producing circuit indicated generally at 33which is capable of generating pulses of considerably higher currentvalue than the pacemaker illustrated by FIGURE 1. The pulse producingcircuit 33 of FIGURE 2 includes all of the circuit components describedin connection with FIGURE 1, and is additionally modified to provide ahigh power output. This modification includes a transistor amplifier 26having a collector electrode 27, a base electrode 28, and a groundedemitter electrode 29. An emitter resistor 30 is inserted between theemitter electrode 17 of the transistor 14 and the source of groundpotential, while the base electrode 28 of the transistor 26 is directlycoupled to the emitter 17' of the transistor 14. The source ofunidirectional voltage 23 furnishes voltage to the collector of thetransistor 14' through the primary winding 18' of the transformer 19' inthe manner described in connection with FIGURE 1. A collector resistor31 is connected in the circuit between the unidirectional voltage source23 and the collector 15' of the transistor 14', so that power is alsofurnished to the collector 27 of the transistor 26. The output lead 24'is connected from the collector 27 of the transistor 26 to a spot on theventricular wall of a human heart, instead of being connected to thecollector 15' of the transistor 14' as described in connection withFIGURE 1. A storage capacitor 32 is provided in the circuit between thecollector 27 of the transistor 26 and a reception point on theventricular wall of the diseased heart.

The pulse forming circuit 33 of FIGURE 2 operates in much the samemanner as the circuit 10 of FIGURE 1, with the exception that the outputpulse from the transistor 14' is amplified by the transistor 26 prior toits transmission to the diseased heart undergoing treatment. When acurrent pulse passes through the transistor 14' in the manner describedin connection with FIGURE 1,

current is caused to flow through the emitter resistor 30, thus causinga positive voltage pulse to appear at the emitter 17 of the transistor14'. This positive pulse is applied to the base 28 of the transistor 26,causing it to saturate and provide a very low impedance path from thecollector 27 through the transistor 26 to ground. This, in effect,connects the storage capacitor 32 directly across a section of cardiactissue, and the storage capacitor discharges into the cardiac tissueinitiating a ventricular contraction. When the current through thetiming transistor 14' is cut-01f in the manner described in connectionwith FIG. 1, the voltage at the emitter 17' drops to reference groundpotential, causing the transistor 26 to go quickly from saturation tocut-off. This change of state of the transistor 26 produces a very highimpedance between the collector electrode 27 and the emitter electrode29 which effectively disconnects the capacitor 32 from the controlledsection of cardiac tissue. The storage capacitor 32 will now rechargethrough the collector resistor 31 to the unidirectional referencepotential of the potential source 23' in preparation for the next outputpulse.

In actual use, the circuit 33 of FIGURE 2 produces a pulse amplitude of10 milli-amperes, a pulse length of one millisecond, and a repetitionrate of one pulse per second. The average battery drain under theseconditions is approximately 10 micro amperes for the transistor 26 and 2micro amperes for the timing transistor 14. Thus over a period of oneyear or approximately 8750 hours, a total of milli-ampere hours will berequired. Thus a 600 milli-ampere hour battery pack will supply overfive years of continuous operation, and such a battery pack, along withthe circuits described in conjunction with FIGS. 1 and 2 and theenvelope and heart connections illustrated in FIG. 3, has proved to beof sufficient size and weight so as to be suitable for permanentimplantation in the human body.

It will be readily apparent to those skilled in the art that the presentinvention provides a novel electronic cardiac pacemaker which may beimplanted within the human body in its entirety to effectively controlthe action of a diseased heart for a prolonged period without thenecessity of external power supplies. The arrangement and types ofcomponents utilized within this invention may be subject to numerousmodifications well within the purview of this inventor who intends onlyto be limited to a liberal interpretation of the specification andappended claims.

I claim:

1. An electronic cardiac pacemaker for performing heart controlfunctions comprising, in combination, a battery powered, transistorized,pulse producing circuit cast in a potting compound, a thin, wafer-likeenvelope formed about said pulse producing circuit, a pair of spacedelectrodes for contacting a section of cardiac tissue, and transmissionmeans extending between said pulse producing circuit and said spacedelectrodes, said envelope, electrodes, and transmission means beingconstructed from material compatible with the environment of the humanbody to permit their implantation therein.

2. The invention of claim 1 wherein said thin, waferlike envelope andtransmission means are covered with material of the class comprisingsilicone rubber.

3. An electronic cardiac pacemaker for performing heart controlfunctions comprising, in combination: a miniaturized pulse generatingmeans cast in a potting compound, said pulse generating means includinga transistor oscillator having emitter, base, and collector electrodes,a source of unidirectional potential connected to said collectorelectrode, a ground reference source connected to said emitterelectrode, a timing circuit connected to said base electrode, and aninductive feedback coupling between said timing circuit and saidcollector electrode, said timing circuit initiating intermittentconduction of said transistor to provide timed output pulses at saidcollector electrode, output means electrically connected to saidcollector electrode and to said ground reference source to supply saidtimed output pulses to a section of cardiac tissue, said output meansincluding a pair of spaced electrodes for contacting a section ofcardiac tissue and transmission means extending from said collectorelectrode to one of said spaced electrodes and from said groundreference source to the remaining one of said spaced electrodes, and anenvelope of thin, waferlike construction to permit the completeimplantation thereof between the skin and rib cage of the human body,said envelope encasing said pulse generating means and, with said spacedelectrodes and transmission means, being constructed of a materialcompatible with the internal environment of the human body.

4. An electronic cardiac pacemaker for performing heart controlfunctions comprising, in combination: a miniaturized pulse generatingmeans cast in a potting compound, said pulse generating means includinga transistor oscillator having emitter, base, and collector electrodes,a source of unidirectional potential connected to said collectorelectrode, a ground reference source connected to said emitterelectrode, a timing circuit connected to said base electrode, and aninductive feedback coupling between said timing circuit and saidcollector electrode, said timing circuit initiating intermittentconduction of said transistor to provide timed output pulses at saidemitter electrode, a transistor amplifier having a collector electrodeconnected to said source of unidirectional potential, an emitterelectrode connected to said ground reference source, and a baseelectrode connected to receive the timed output pulses from the emitterelectrode of said transistor oscillator, said timed output pulsesdriving said transistor amplifier between states of saturation andcutoff, a storage capacitor connected to the collector electrode of saidtransistor amplifier, said storage capacitor being controlled by saidtransistor amplifier to discharge a pulse potential when said amplifieris in a state of cutoff and to charge directly from said source ofunidirectional potential when said amplifier is in a saturated state,output means electrically connected to said storage capacitor and saidground reference source to supply said pulse potential to a section ofcardiac tissue, said output means including a pair of spaced electrodesfor contacting a section of cardiac tissue and transmission meansextending from said capacitor to one of said spaced electrodes and fromsaid ground reference source to the remaining one of said spacedelectrodes, and an envelope of thin, wafer-like construction to permitthe complete implantation thereof between the skin and rib cage of thehuman body, said envelope encasing said pulse generating means and, withsaid spaced electrodes and transmission means, being constructed of amaterial compatible with the internal environment of the human body.

References Cited in the file of this patent UNITED STATES PATENTS DiVette Ian. 19, 1960 Vibber Feb. 23, 1960 OTHER REFERENCES

